Scientific evidence suggests that many adolescents with acute lymphoblastic leukemia (ALL) do not take their medication in accord with their prescribed treatment regimens. Such nonadherence has several undesirable clinical and scientific consequences:(1) mortality and morbidity due to relapse; (2) problems in the validity of data concerning clinical trials of medication treatment, which if undetected, may create the potential for iatrogenic toxicity. However, there are little scientific data concerning the efficacy of psychological interventions that have been designed to limit the prevalence and impact of nonadherence to ALL treatment. To address this important scientific need, this study will conduct a randomized clinical trial (RCT) with 170 adolescents with ALL to evaluate a family centered, problem-solving intervention (FPST) to promote adherence to oral medication treatment. This problem solving intervention will be compared with basic psychological care. The proposed intervention model is novel in its integration of three key components derived from theory and research on adherence to treatment with pediatric chronic illnesses and cast within the developmental context of families with adolescent children. These components are: 1) training in collaborative problem solving and effective parent-adolescent communication to reduce barriers that interfere with adherence to oral medication treatment; 2) promotion of adolescents' active participation in and motivation for the management of ALL therapy; 3) emphasis on parental support and adolescent adherence to treatment that is consistent with the developmental needs of the adolescent. The primary hypothesisof the proposed study is as follows: a family-centered problem solving intervention will result in improved adherence to prescribed oral medication 6MP and Decadron among adoelscents with ALL comparedwith basic psychosocial care. We anticipate that the proposed study will identify effective strategies to promote adherence among adolescents with ALL and will potentially lead to improved medical outcomes for these adolescents. Second, we anticipate that the principles of the intervention model will generalize beyond ALL to adolescents with other forms of cancer as well as other chronic conditions and their families. Finally, improving adherence to oral medication during maintenance therapy for adolescents who participate in clinical trials would improve the validity of the data drawn from those investigations.